RESISTANCE PRIMARY SENSOR FROST PROTECTION

Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4

Set Multimeter to Resistance

Remove the connector from the primary sensor

Measurement:

Measure the resistance across the primary sensor's pins.
The resistance depends on temperature and should conform to the table below:

Temperature °C	Resistance in kOhms
0 - 10	28.9 - 17.1
10 - 20	17.0 - 12.2
20 - 30	12.0 - 8.2
30 - 40	8.5 - 5.5
40 - 50	5.8- 3.8
50 - 60	4.0 - 2.7
60 - 70	2.9 - 2.0
70 - 80	2.1 - 1.4

Note:
If the temperature of the boiler drops below 4°C the boiler will fire and run until the temperature increases to 30°C. This is the in-built frost protection and is normal operation.